Switching at the Core?

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Nov 12th, 2007
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Recently, someone I know was tasked with creating a design for a next generation server farm at a new data center. He provided a drawing that depicted a switched access layer, a distribution layer and a core -- the typical Cisco hierarchical model.

The parts I thought were strange were the following:

1. No routed connection between the pair of distribution layer switches. Instead, he shows only a 40G L2 etherchannel between them.

2. No L3/routed connected between the pair of core switches. Instead, he shows only an 80-G L2 etherchannel between them.

3. He also extended the switching domain all the way up to the core with 40-G L2 Trunks that are dual-homed from each distribution switch to each of a pair of core switches.

4. No L3 routed connections at all between the distribution layer and the core.

This design approach looks like it violates some very basic internetworking design principles. Am I wrong?

Attached is the drawing he provided. Where it says "network core", he provides a separate drawing that shows two 6509s connected to each other with an 80-G etherchannel.


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